Which type of joint allows movement around only one axis?

• A. Ball-and-socket joint
• B. Pivot joint
• C. Saddle joint
• D. Hinge joint

Answer: (D)

Verified step by step guidance

1. Step 1: Understand the concept of joint types in the human body. Joints are classified based on their structure and the type of movement they allow. Examples include hinge joints, ball-and-socket joints, pivot joints, and saddle joints.
2. Step 2: Recall the definition of a hinge joint. A hinge joint is a type of synovial joint that allows movement primarily in one plane, similar to the motion of a door hinge. This movement is around a single axis, enabling flexion and extension.
3. Step 3: Compare the hinge joint to other types of joints mentioned in the problem. For example, ball-and-socket joints allow movement in multiple axes (e.g., shoulder joint), pivot joints allow rotational movement around a single axis (e.g., the atlantoaxial joint in the neck), and saddle joints allow movement in two planes (e.g., the thumb joint).
4. Step 4: Identify examples of hinge joints in the human body. Common examples include the elbow joint and the knee joint, which allow flexion and extension around one axis.
5. Step 5: Conclude that the correct answer is 'hinge joint,' as it is the only type of joint listed that allows movement around only one axis.